This invention relates to the method of making a hydrostatic cylinder block. More specifically, and without limitation, this invention relates to a method of breaking a hydrostatic cylinder block down into its basic geometries and parts to produce a new and more efficient hydrostatic cylinder block manufacturing process.
In general, most hydrostatic cylinder blocks that are used in medium and heavy duty applications are produced by machining a single piece of raw material into its final shape. This manufacturing process is not only expensive but limits the function and the dimensional capability of the design. The high manufacturing costs stem from the numerous processing steps, high capital investment, and ongoing production costs. Cylinder block concepts that completely rely on machining to obtain net shape impose design limitations because of the inability to properly machine due to geometric constraints, (i.e., honing of cylinder block bores cylindrically, surface finish, and machine bore undercuts) causing production to be difficult and expensive.
The current process for a heavy duty hydraulic cylinder block is performed in ten separate operations. The manufacturer must first rough the turn block and drill bores for the cast-on-bronze process. Then the manufacturer must cast bronze on the bottom of the cylinder block. Next, in two separate operations, a manufacturer must turn the overall shape of the block. The next step is to ream the bushing bores. After reaming the bushing bores, kidneys must be milled into the bushing bores. Then the manufacturer has to press bushings in the bores and finish the machine bushing bores. Finally, one must broach the block splines and lap the cylinder block face onto the block, thus creating the heavy duty hydrostatic cylinder block.
The complex geometries and functional requirements of a cylinder block have typically forced manufacturers to resort to a large number of manufacturing operations. In general, today""s cylinder block designs limit manufacturing to processes that are both costly and inefficient. To overcome the obstacle of a ten step process, a new concept has been conceived that breaks a standard cylinder block into basic geometries (components) that can be manufactured cost efficiently through various near net shaping technologies.
Near net shape processing achieves the final dimensions of a desired shape with minimal machining. Examples of near net shape technologies include casting, stamping, injection molding, and sheet metal working. For instance, in an injection molding process a mold of the dimensions needed for the construction of a metal product is created. Liquid metal is then injected into the mold and after some processes is cooled to create a machine part. This is called near net shaping because during the process the metal or material being used changes size and shape slightly during the cooling process. Therefore, near net shaping is not always perfectly accurate; however, because of recent advances in the near net shaping art, near net shaping is now precise enough to create hydrostatic cylinder blocks components of desired tolerances.
When machining hydrostatic cylinder blocks the machinery used to machine the blocks becomes worn, making maintaining dimensional tolerances very difficult. This exact machining takes a lot of time and can be very damaging to tools. Therefore, a process that would limit the amount of machining preformed on the block would greatly increase accuracy of tolerances and lower manufacturing costs.
Thus, it is a primary object of the present invention to provide a method of making a hydrostatic cylinder block that improves upon the state of the art.
Another object of the present invention is to breakdown a standard hydrostatic cylinder block into basic geometries that can be cost efficiently manufactured through various near net shaping processes.
Yet another object of the present invention is to efficiently transfer load and torque through the assembly.
A further object to the present invention is to utilize either by metal or conventional tubing to form cylinder bores.
Yet another object of the present invention is to join technology by discharge resistance welding, specifically to join piston bores to a base plate and a drive shaft to the same base plate.
A further object of the present invention is the integration of a polygon drive spline into a compact package. Yet a further object of the present invention is to increase torque carry capacity.
A further object of the present invention is to allow a manufacturer to have the ability to fine grind piston boresxe2x80x94hone/super finish operation.
A final object of the present invention is to be able to cost effectively add bore undercuts to a hydrostatic cylinder block.
These and other objects, features, or advantages of the present invention will become apparent from the specification and claim.
This invention relates to a hydrostatic cylinder block created by breaking the block into four basic geometries: a base plate, a drive shaft, piston bores, and a torque ring. Each can be produced using near net shape technologies. This minimizes the amount of machining that needs to occur before the block is in working form. This concept eliminates many of the machine operations and increases design and manufacturing flexibility. By using the geometries, the ten step operation of hydrostatic cylinder block manufacturing is now broken down into a three step operation. First, a manufacturer must join the four components. Then a manufacturer must hone the cylinder block bores and lap the cylinder block face onto the block. Thus, a heavy duty hydrostatic cylinder block can now be manufactured more efficiently and more inexpensively.
The present invention also provides for a hydrostatic cylinder block created by the method described. The block has a base plate with a center opening and bores located radially around the center opening. Each bore has a kidney-shaped opening. The block also has a drive shaft adapter that has an end adapted to mate with the base plate and an internal spline exterior adapted to receive a plurality of cylindrical piston bores. The block also has a torque ring that has a plurality of elongated arcuate grooves on its inner surface that matingly engage the piston bores.